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    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
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<body>
    <script>
        let name = "jack";
        console.log(name);  //jack

        //Uncaught SyntaxError: Identifier 'name' has already been declared
        // let name = "lili";   //重复声明变量 不允许 会报错

        console.log(name);
    </script>
</body>
</html>